Silicates, such as sodium and potassium silicates, are shipped in a glass form to end users desiring a liquid solution of silicate. The glass form is easy to manufacture and ship and can easily be dissolved to obtain the desired solution. For these reasons, the glass form is a desired way of delivering the silicate. In the past, molten silicate glass was poured into large trays, allowed to cool, and dumped into a hopper. The large glass pieces from the trays were fragile and would break and shatter, producing very fine particles (fines). The breakage and shattering could occur from the fall into the hopper, but would also occur spontaneously, due to internal stresses built up during the cooling of the untempered glass.
Once shattered, a glass dust forms which can adhere to the sides of the tank and equipment containing the dissolving solution. The adhered dust may not fully dissolve and can build up, clogging the dissolving equipment. Further, if the amount of dust is great, the minute size of the dust particles makes it difficult to handle. This difficulty in handling holds true for particle sizes of broken or shattered glass which may be slightly larger than dust size particles.
Forming a silicate glass form which does not easily thermally shatter or mechanically break will significantly reduce the amount of dust and particulate matter formed during the manufacture, storage and shipping of the silicate glass form to an end user. One way to reduce breakage or shattering is to temper the glass by rapid cooling in such a way that all surfaces of the glass form are under a high state of compression after the silicate glass form reaches room temperature. These compressive stresses are counter-balanced by tension in the central layers of the silicate glass form. A piece of silicate glass so tempered cannot be broken unless sufficient force is applied to overcome the compression of the surface and create tension or unless the tensile strength of the interior is exceeded. Maximum strength is then achieved by developing the highest compressive forces at the surfaces which will not cause the counterbalancing tension in the central layers to exceed the tensile strength of those layers. This rapid cooling, non-shattering concept is explained in Volume II of the Handbook of Glass Manufacture, Copyright 1974, Section 14, Article 12, "Increasing the Strength (of Glass) by Tempering".
However, the glass must be properly shaped to handle the external compressive and internal tensile forces. In the past, several different approaches have been tried which consisted mainly of the manufacture of square (four sided) pyramids between 11/2" and 3" on a side. However, these pyramids nevertheless develop internal stresses, concentrated mainly at the corners, which leads to a significant chance of breakage. Occasionally, such a pyramid will explode spontaneously without first being exposed to any external disturbance, due to these internal stresses. As a result, a large amount of fines (very small particles which tend to clog the silicate dissolving machinery) occur as a result of producing glass by this method. Therefore, there is a need to produce silicate glass without producing fines.